1. Field of Invention
The present invention relates to a device and method for switching wavelength division multiplexed light signals using modulated emitter arrays.
2. Description of Related Art
Optical communication systems are a substantial and rapidly growing part of communication networks. The expression xe2x80x9coptical communication system,xe2x80x9d as used herein, relates to any system that uses optical signals to convey information across an optical transmission device, such as an optical fiber. Such optical systems may include, but are not limited to telecommunication systems, cable television systems, and local area networks (LANs).
While the need to carry greater amounts of data on optical communication systems has increased, the capacity of existing transmission devices is limited. Although capacity may be expanded, e.g., by laying more fiber optic cables, the cost of such expansion is prohibitive. Consequently, there exists a need for a cost-effective way to increase the capacity of existing optical transmission devices.
Wavelength division multiplexing (WDM) has been adopted as a means to increase the capacity of existing optical communication systems. In a WDM system, plural optical signals are carried over a single transmission device, each channel being assigned a particular wavelength.
An essential part of optical communication systems is the ability to switch or route signals from one transmission device to another. Designers have considered using bubbles that are capable of changing their internal reflection for switching optical signals. However, this technique is unable to switch multiple wavelengths individually. Furthermore, both of these devices have limited switching speeds, in the range of 10 kHz for the mirror devices and in the range of 100 Hz for the bubble devices.
Micro-electromechanical mirrors are capable of switching optical signals. However, these mirrors have not been utilized in a way that would allow them to be used in a WDM system.
Other switching approaches, such as the approach disclosed in U.S. Pat. No. 4,769,820, issued to Holmes, can switch data at GHz rates, which is effectively switching at GHz transition rates. However, this approach requires substantial optical switching power, has potential cross talk, and cannot resolve wavelength over-utilization issues. What is needed is a means for switching wavelength division multiplexed signals that is capable of doing so at high speeds with no cross talk and requires low switching power.
1. Advantages of the Invention
One advantage of the present invention is that it is able to switch signals of different wavelengths.
Another advantage of the present invention is that it is able to switch at high speeds.
A further advantage of the present invention is that it does not require high power.
Another advantage of the present invention is that it does not suffer from crosstalk.
Another advantage of the present invention is that it is able to switch between wavelengths and fibers to avoid transmission device or wavelength over-utilization.
Another advantage of the present invention is that it is able to broadcast to multiple transmission devices or couplers simultaneously.
A further advantage of the present invention is that it is able to regenerate and restore signals.
An additional advantage of the present invention is that it can transmit through air or other intervening media to a receiver without a costly or slow electrical interface.
These and other advantages of the present invention may be realized by reference to the remaining portions of the specification, claims, and abstract.
2. Brief Description of the Invention
The present invention comprises an optical switch element for use with at least one source and a plurality of targets. The source is adapted to transmit an optical signal to the optical switch element and the targets are adapted to receive the optical signal from the optical switch element.
The optical switch element comprises a beam splitter, first and second wave plates, and first and second micro-mechanical mirrors. The beam splitter is adapted to transmit light in a first predetermined polarization and reflect light in a second predetermined polarization. The first wave plate is positioned between the source and the beam splitter and it is adapted to transmit light in the polarization that is reflected by the beam splitter, wherein light transmitted by the source passes through the wave plate and is reflected by the beam splitter.
The first micro-electromechanical mirror is positioned to receive light reflected by the beam splitter and it is adapted to selectively reflect light in a plurality of paths, the paths corresponding to the positions of the plurality of targets. The second micro-electromechanical mirror is positioned to receive light reflected by the first micro-electromechanical mirror and it is adapted to reflect light in a path, the path being a predetermined orientation relative to at least one of the targets.
The second wave plate is positioned between the second micro-electromechanical mirror and the beam splitter and it is adapted to transmit light in the polarization that is transmitted by the beam splitter, wherein light reflected by the second micro-electromechanical mirror passes through the second wave plate and the beam splitter and is transmitted to a target.
The above description sets forth, rather broadly, the more important features of the present invention so that the detailed description of the preferred embodiment that follows may be better understood and contributions of the present invention to the art may be better appreciated. There are, of course, additional features of the invention that will be described below and will form the subject matter of claims. In this respect, before explaining at least one preferred embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of the construction and to the arrangement of the components set forth in the following description or as illustrated in the drawings. The invention is capable of other embodiments and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein are for the purpose of description and should not be regarded as limiting.